What is God's Sovereign Grace?...

God's sovereign grace is just this...
He says...
"I will have mercy on whom I will have mercy,
and I will have compassion
on whom I will have compassion.
So then it is not of him that willeth, nor of him that runneth,
but of God that sheweth mercy".
Romans 9:15; Exodus 33:19

Because mankind is carnally minded, born into sin,
in bondage to sin, helpless in his own ability...
only God can bring about the salvation of an individual.
Only God.
How?
He regenerates the heart of whom He will have mercy on.
He makes that heart willing in the day of His power...
"Thy people shall be willing in the day of Thy power..."
Psalms 110:3

The power of what?
The power of His arm of salvation...
For of Jesus Christ, our Lord, it was said...
"And He saw that there was no man, and wondered that there was no intercessor: therefore His arm brought salvation unto Him;
and His righteousness, it sustained Him."
Isaiah 59:16

God alone gets all the credit of saving a soul.

Blessed be the Lord God.
May He show His grace and mercy to you.